import type { ContextEvent } from "@earendil-works/pi-coding-agent";
type AgentMessage = ContextEvent["messages"][number];

const WEB_TOOL_NAMES = new Set(["web_search", "web_fetch", "web_fetch_read"]);

function stringField(value: unknown, key: string): string | undefined {
  if (!value || typeof value !== "object") return undefined;
  const field = (value as Record<string, unknown>)[key];
  return typeof field === "string" && field ? field : undefined;
}

function clearedReceipt(toolName: string, details: unknown): string {
  const artifactId = stringField(details, "searchId")
    ?? stringField(details, "fetchId")
    ?? stringField(details, "artifactId");
  const reportPath = stringField(details, "reportPath");
  if (toolName === "web_search") {
    if (reportPath) {
      return `[Previous web search content cleared from active context. report_path=${reportPath}; use read(path, offset, limit) if needed.]`;
    }
    return artifactId
      ? `[Previous web search content cleared from active context. search_id=${artifactId}; report path unavailable.]`
      : "[Previous web search content cleared from active context.]";
  }
  return artifactId
    ? `[Previous fetched web content cleared from active context. fetch_id=${artifactId}; use web_fetch_read if needed.]`
    : "[Previous fetched web content cleared from active context.]";
}

/** Replaces prior-user-turn web payloads while preserving every tool-call/result pair. */
export function pruneHistoricalWebResults(messages: AgentMessage[]): AgentMessage[] {
  let latestUserIndex = -1;
  for (let index = messages.length - 1; index >= 0; index -= 1) {
    if (messages[index]?.role === "user") {
      latestUserIndex = index;
      break;
    }
  }
  if (latestUserIndex < 0) return messages;

  return messages.map((message, index) => {
    if (
      index >= latestUserIndex ||
      message.role !== "toolResult" ||
      message.isError ||
      !WEB_TOOL_NAMES.has(message.toolName)
    ) {
      return message;
    }
    return {
      ...message,
      content: [{ type: "text", text: clearedReceipt(message.toolName, message.details) }],
    };
  });
}